Nondestructive method for testing batteries



United States Patent 3,440,015 NONDESTRUCTIVE METHOD FOR TESTINGBATTERIES Frederic M. Bowers and Regina D. Wagner, Silver Spring,

Md., assignors to the United States of America as represented by theSecretary of the Navy No Drawing. Filed June 23, 1965, Ser. No. 466,486Int. Cl. G01r 31/16 US. Cl. 23-230 11 Claims ABSTRACT OF THE DISCLOSUREA method for determining the capacity of a battery having a silver oxideelectrode wtihout a destructive discharge by the steps of: placing anumber of electrodes that have been manufactured and processed like thatin the battery in a separate sealed compartment in the battery; removingone of the number of electrodes from the sealed compartment; andanalyzing the removed electrode for Ag, AgO, and Ag O content by aprocess including (1) separating the silver oxides from the Ag in aportion of the removed electrode having a known weight by, first,treating the portion with NH OH to solubilize the silver oxides into asoluble silver amine complex and, second, separating the soluble silveroxides from the Ag by filtration, (2) weighing the remaining Ag todetermine the Ag content, (3) determining the Ag content in the silveroxides by gravimetric chloride, (4) adding a saturated solution of KI toanother portion of the removed electrode having a known weight to reactwith the AgO to produce I which, in turn, reacts quantitatively with theAg", (5 determining the amount of I liberated from the amount of I thatreacted with the Ag and the amount of I remaining in solution asmeasured by Na S O titration, thereby determining the AgO content, and(6) determining the Ag O content from the Ag content of the silveroxides and the AgO content, whereby the capacity of the battery may bedetermined by the chemical composition of said removed electrode.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

This invention pertains to both a novel method for indicating thecapacity of a battery and to a novel method for determining the silverand silver oxides content of a sample. More particularly, it pertains toa nondestructive method for determining the capacity of a battery bychemical analysis and more specifically to a method for determining thecapacity of a battery having a silver oxide electrode by determining itssilver and silver oxides content.

Large stockpiles of batteries are often maintained for many purposes,and it would be advantageous to have an effective method for determiningtheir capacity without prior activation and/or destructive discharge.For example, the fleet maintains a large stockpile of primary batteriesfor missiles and torpedoes and, in order to prevent an in-weapon use ofa defective battery, the state of charge should be periodically tested.The state of charge has been determined by measuring voltage andcurrent, but this necessitates activating and discharging the 3,440,015Patented Apr. 22, 1969 ice battery; and, since such batteries cost fromabout 3 to 4 thousand dollars, this method is not practical.Furthermore, it does not indicate the condition of the electrode whichalso affects the capacity of the battery.

Accordingly, it is an object of this invention to provide anondestructive method for indicating the state of charge of a battery.

Another object of this invention is to provide a method for determiningthe capacity of a battery by chemical analysis.

A further object is to provide a novel method for determining the silverand silver oxides (AgO and Ag O) content of a sample.

Still another object is to provide a method for determining the capacityof a battery having a silver oxide electrode by analyzing its silver andsilver oxides content.

These and many other objects will become readily apparent from readingthe following detailed description of the invention.

The objects of this invention are accomplished by packaging electrodesthat have been manufactured and processed exactly like those in thebattery in a separate sealed compartment in the battery so that theywill be subjected to the same environments as those in the battery.Whenever it is necessary to determine the capacity of the battery, anelectrode is removed from the compartment, the compartment rescaled, andits chemical composition analyzed. The state of charge of the batterycan then be determined from a previously prepared graph that plots therelationship between the capacity of the battery (ampere-hours) and thecomposition of the electrode. Alternatively, a theoretical calculationof the capacity of the battery can be made by Faradays law, since theweight and composition of the electrode are known.

In a battery that has a silver oxide electrode, the amount of silveroxides and silver present in the electrode will indicate the capacity ofthe battery according to the following reactions:

2Ag0 :Agzo Oz (Fully (Partially Charged) Charged) A220 I, 2Ag+ Oz(Partially (Dis- Charged) charged) The amounts of these components maybe determined by the novel silver-silver oxides analysis of thisinvention and the capacity of the battery may subsequently be determinedfrom a previously prepared graph.

The novel silver-silver oxides analysis of this invention comprises thefollowing two steps:

1) Determining the amounts of silver metal and total silver present asoxides by separating the silver from the silver oxides.

(2) Determining the amount of AgO present by an iodometric determinationof the oxidizing power of the sample.

A sample prepared from one of the additional silver oxide electrodes isdivided into four portions with two portions being used in each step. Inthe first step, ammonium hydroxide is added to one of the portions toconvert the silver oxides to a soluble amine complex. The solublecomplex is separated from the solid silver by filtration and since it isunstable it is immediately decomposed by neutralization in order toprevent an explosion. The total silver in the separated oxides isdetermined by gravimetric chloride and the silver metal content isdetermined by weighing the separated solid silver.

In the second step, a saturated solution of potassium iodide which hadbeen added to another portion of the sample is oxidized by the argenticoxide according to reaction (1) and reacts with the argentous oxideaccording to reaction (2).

The iodine liberated by reaction 1) reacts with the silver metal presentaccording to reaction (3).

Reaction (3) is quantitative when the concentration of potassium iodideis high enough to keep all the silver iodide dissolved. This reactionmust take place quantitatively for the analysis of the sample to beaccurate and if there is not suflicient iodine present to react with allof the silver present, more iodine must be added. After the reactionsare complete, the amount of iodine that has not reacted is determined bytitration with sodium thiosulfate.

The information'obtained from the above procedure is used to calculatethe amounts of Ag, AgO, and Ag O present in the sample. The amount ofsilver present is calculated from the weighing of Step 1; the AgO, fromthe total amount of iodine liberated in reaction (1) (the sum of theiodine remaining in the solution as determined from the titration andthe iodine that reacted quantatively with the known amount of silver,less any iodine added); and the Ag O, from the known amount of silverpresent as oxides (Step 1) and the known amount of AgO (Step 2).

The invention may be more fully understood by reference to the followingexamples which are presented by way of illustration and are not to beconstrued as limiting the invention:

EXAMPLE I The following reagents are used? (1) Analytical quality nitricacid, hydrochloric acid, sulfuric acid and iodate free analyzed-gradepotassium iodide.

(2) A 0.1 N sodium thiosulfate solution is prepared by idding 25 g. ofreagent grade sodium thiosulfate crystals to 1 liter of freshly boileddistilled water containing 2-3 g. of borax crystals as a preservative.The solution is standardized with pure potassium iodate.

(3) A 0.1 N iodine solution is prepared by adding 6.5 g. of resublimediodine to 500 ml. of distilled water containing 12 g. of potassiumiodide. This solution is standardized just prior to and immediatelyafter its use.

(4) A Sterox solution is prepared by adding approximately 0.5-1.0 ml.Fisher 1% Sterox solution to 500 ml. of distilled water.

Sample preparation A sample electrode is wrapped in an envelope ofglassine paper and the active material is worked loose from the grid.The silver-silver oxides mixture is transferred into an agate mortar andthe agglomerates are broken by gentle crushing with an agate pestal.(Vigorous grinding or milling must be avoided because this alters thecomposition of the sample.) The sample is transferred to a small glasscontainer with a tight fitting cap and it is mixed thoroughly byvigorous shaking. The mixture should be shaken prior to the removal ofeach aliquot to avoid obtaining a sample which is not homogeneous due tothe settling of the larger particles. It is not necessary that thesample be moisture free prior to analysis, since the silver containingcomponents are determined independently and the amount of impurities andmoisture can be obtained by ditference. However, the sam le must be dryenough for an accurate determination of its weight.

The analysis of the sample is performed according to the followingprocedure:

Step 1 Weigh a 0.250.4 g. portion of the sample directly into a 30 ml.fine porosity filter crucible, which has previously been brought to aconstant weight. Seat the crucible above a 500 ml. filtering flaskcontaining 10 ml. 1:1 HNO in a manner which permits the quantitativerecovery of the filtrate. Slowly pour 15 ml. of 1:20 NH OH into thecrucible and allow the mixture to stand while the oxides of silverdissolve. After approximately one-half hour, apply a gentle suction tothe filtering flask and remove most of the NH OH solution from thecrucible. Slowly pour another 15 ml. of 1:20 NH OH into the crucible andallow the mixture to stand for an hour. The solids in the crucibleshould be stirred with a stream of distilled water occasionally tofacilitate the dissolution of the Ag O. (Caution: Do not stir themixture in the crucible with a stirring rod; this may cause an explosionof the silver amine complex.) The removal and replenishment of the NH OHsolution should be continued until all the silver oxide has dissolved.(Two 15 ml. portions of the NH OH solution should be sufiicient fordissolving the oxides in most samples; however, when the sample containslarge amounts of Ag O, additional quantities of NH OH solution arerequired.) When the silver oxides have dissolved, wash the silver metalin the crucible twice with 10 ml. of 1:20 NH OH and several times withdistilled water. Dry the crucible to a constant weight and determine theweight of the silver metal.

Quantitatively transfer the filtrate to a 400 ml. beaker. The solutionshould be acidic; if not, acidify with 1:1 HNO Add 2 ml. of concentratedHCl to precipitate the silver as silver chloride. Heat the suspensionnearly to boiling and then allow it to stand in the dark for a minimumof one hour. Collect the precipitate quantitatively in a previouslyweighed fine porosity filter crucible. Dry the crucible to a constantweight and determine the weight of the silver chloride.

Step 2 Weigh a 0.25-0.4 g. portion of the sample into a ml. iodineflask. Add 10 g. of potassium iodide and rinse down the sides of theflask with approximately 5 ml. of Sterox solution a wetting agent thatincreases the rate of reaction between the silver and iodine. Swirl thefiask until all the black silver oxide powder has dissolved. Add 10 ml.of 1 N H 50 and swirl the flask in subdued light for about 3-5 minutesto allow the oxidation of the silver metal to occur.

Begin the addition of Na S- O titrant. Stop the titration prior to itscompletion and examine the solution to determine if all the silver metalhas been oxidized. If particles of silver metal can be seen on thebottom of the flask, swirl the flask until they are dissolved and thencontinue the titration until one drop titrant removes the iodine color.

If the number of milliequivalents of silver metal present in the sampleis greater than or equal to the number of milliequivalents of AgO, itwill be necessary to pipet a known volume of the standardized 0.1 Niodine solution into the flask. If silver metal remains unoxidized whenthe iodine color becomes pale, the addition of iodine is necessary. Wheniodine solution is added to the unknown an additional quantity of KI,approximately 5 g. KI for each 10 ml. of iodine solution, must also beadded in order to keep all of the AgI in solution. The iodine can beadded at any stage in the above procedure after the silver oxides havedissolved.

Because of the air oxidation of KI in acid solution, the volume of Na SO used must be corrected to the volume necessary to titrate a blank. Ablank should be run with each of the duplicate analyses.

The composition of the sample may be calculated from the informationobtained above in the following manner:

CALCULATION OF SAMPLE COMPOSITION (meq. I liberated) (g. AgOlmeq.)X100Percent Ago: (Sample Wt. in g.)

meq. I liberated= (men. I found by titration) +(meq. I" used in Agoxidation)(meq. 1 added) (Sample WU (percent Ag/100) 1 e [(meq. 1rounm-W- (mcq. 1 added)](0.12387) Percent Ago 0.10787 (Sample Wt in g.)

3. Calculation of percent AgzO:

Percent AgzO (sample in Wt. Ag due to AgO =[(Sarnple Wt!) (percentAg/100)1[At.

Percent AgzO [(Wt. Ag in oxides)-(Wt. Ag due to Ag0)][M.W. AgzO/2(At. W.Ag)

([(Wt. AgCl) (.7526)]-[(Sample Wtj) (percent Ago/100) (.8708)]} (1.0643)X100 (Sample Wt. in g.)

No'rE.-Sample Wt. =Wt. of sample used in Step I. Sample Wt. =Wt. ofsample used in Step II.

EXAMPLE II I. Analysis for Ag Wt. Tare and sam 1e, 31. 8368 31.0066 Wt.Tare, g a l"? 31. 5805 30. 6904 Wt. Sample, g 0.2563 .3162 Wt. Tare andAg", g... 31. 6163 30. 7354 Wt. Ag, g 0. 0358 0. 0450 Percent Ag 13. 9714. 23

II. Analysis for Ag in Oxides Wt. Tare, g 31:2815 Wt. Tare and AgCl, g31. 6030 Wt. AgCl, g 0. 3215 Wt. Ag (Wt. AgClX.7526), g 0. 2419 III.Analysis for AgO Wt. S and Tare, 5088 0. 5086 Wt. T r fg 0.2422 0. 2511Wt. Sample, g 0.2606 0. 2575 Final Volume N82810:, ml 4. 57 4. 33Initial Volume Nagszo ml..- 0. 08 0. 06 Total Volume Naqsma, ml 4. 49 4.27 Blank Volume, ml 0. 10 0. 10 Corrected Tot Vol 1111.. 4. 39 4. 17 ms.Ag 0. 0379 0.0363

IV. Calculation of Percent Ag() Meg. of 1 found. 0. 5527 0. 5250 Meq. of1 used by A 0. 3486 0. 3365 Tot. meq. 1 liberated. 0. 9013 0. 8615 Gms.AgO 0.1116 0.1067 Percent AgO 41. 85 41. 44 Average 6% V. Calculation ofPercent AgzO Wt. AgO in sample, g 0.1060 0.1315 Wt. Ag due to Ag g----0. 0928 O. 1145 Wt. Ag due to AgzO, g... 0.1042 0.1274 Gms. AgqO 0. 11090. 1356 Percent Agr0. 43. 27 42. 88 Average 43.1%

6 Percent Ag 14.1

Percent AgO 41.6

Percent Ag O 43.1

EXAMPLE III A silver oxide electrode was removed from a battery that wasmanufactured in 1964 by the same company that produced the battery ofExample II and it was analyzed by the procedure of Example I. Theresults were as follows:

Percent-Ag 11.2 Percent AgO Percent Ag O 29.0

The capacity of the battery can be calculated by Faradays Law or from apreviously prepared graph that relates the batterys capacity to theelectrodes composition.

The process of this invention provides a simple means for determiningthe capacity of a battery without a destructive discharge. Since everybattery has a limiting electrode, it is only necessary to analyze thiselectrode to. determine the capacity of the battery. The sealedcompartment, however, should contain both electrodes so that if there isany interaction between the battery electrodes in the dry state theadditional electrodes will be be subjected to the same conditions. Themethod of this invention may be used to determine the capacity of anybattery but it is especially valuable for determining the capacity ofprimary batteries that are stockpiled by the fleet for use in torpedoesand missiles.

The novel silver-silver oxides analysis of this invention solves a longexisting need in the art since heretofore there has been no practicalway to accurately analyze a sample that contains silver, argentic oxideand argentous oxide. Although it has a particular applicability in themethod of this invention for determining the capacity of a battery witha silver oxide electrode, it may be used to determine the silver-silveroxides content of any sample.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood, that within the scope of the appended claims, the inventionmay be practised otherwise than as specifically described.

What is claimed is:

1. A method for determining the capacity of a battery having a silveroxide electrode without a destructive dis charge, comprising the stepsof:

placing at least one additional electrode that has been manufactured andprocessed like that in the battery in a sealed compartment in thebattery;

removing at least one of said additional electrodes from said sealedcompartment; and

analyzing said removed electrode for its content of Ag, AgO, and Ag O bya process including the steps of:

separating the silver oxides from the free silver in a first portion ofsaid removed electrode by: treating said first portion with NH OH tosolubilize said silver oxides and separating said soluble silver oxidesfrom the silver metal, weighing the remaining silver metal, therebydetermining the amount of free silver present, determining the amount ofsilver in said silver oxides by gravimetric chloride, adding a saturatedsolution of potassium iodide to a second portion of said removedelectrode to react with the AgO to produce free iodine, said free iodinereacting quantitatively with said free silver, determining the amount offree iodine liberated from (1) the amount of free iodine that reactedwith said free silver and (2) the amount of free iodine remaining insaid solution measured by titration of sodium thiosulfate, therebydetermining the amount of AgO present, and determining the amount of AgO present from the total amount of silver present as oxides and theamount of AgO present, whereby the capacity of the battery may bedetermined by the chemical composition of said removed electrode.

2. A method for determining the argentic oxide content of an admixtureof free silver (Ag), argentic oxide (AgO) and argentous oxide (Ag O),comprising:

determining the Ag content of said admixture;

adding a saturated solution of potassium iodide (KI) to a portion ofsaid admixture having a known weight to react with the AgO to producefree iodine (I which reacts quantitatively with the Ag to produce silveriodide (AgI); and

determining the amount of I produced from the reaction of KI with AgO byadding the amount of I; which reacted with the Ag to produce AgI to theamount of I remaining in solution.

3. The method of claim 2 wherein the amount of I remaining in solutionis determined by titration with sodium thiosulfate (Na S O 4. The methodof claim 2 wherein the Ag content is determined by a process including:

separating the Ag from the AgO and Ag O in a portion of said admixturehaving a known weight by: treating said portion with ammonium hydroxide(NH OH) to solubilize the AgO and Ag O, and separating the soluble AgOand Ag O from the Ag; and weighing the Ag, whereby the Ag content ofsaid admixture may be calculated.

5. A method for determining the free silver (Ag), argentic oxide (AgO),and argentous oxide (Ag O) content of an admixture of Ag, AgO, and Ag O,wherein the AgO content is determined by the method of claim 2.

6. A method for determining the capacity of a battery having a silveroxide electrode without a destructive discharge, comprising:

placing at least one additional electrode that has been manufactured andprocessed like that in the battery in a sealed compartment in thebattery;

removing at least one of said additional electrodes from said sealedcompartment; and

analyzing said removed electrode for its free silver 8 (Ag), argenticoxide (AgO), and argentous oxide (Ag O) content by the method of claim5.

7. A method for determining the argentic oxide content of an admixtureof free silver (Ag), argentic oxide '(AgO), and argentous oxide (Ag O),comprising:

determining the Ag content of said admixture; adding a saturatedsolution of potassium iodide (KI) to a portion of said admixture havinga known weight to react with the AgO to produce free iodine (I whichreacts quantitatively with the Ag to produce silver iodide (AgI); addinga sufficient amount of I solution to react completely with the remainingAg to produce additional AgI; and

determining the amount of I produced from the reaction of KI with AgO byadding the amount of I which reacted with Ag to produce AgI to theamount of I remaining in solution and subtracting the amount of I addedby the adding of the I solution.

8. The method of claim 7 wherein the amount of I remaining in solutionis determined by titration with sodium thiosulfate (Na S O v 9. Themethod of claim 7 wherein the Ag content is determined by a processincluding:

separating the Ag from the Ag-O and Ag O in a portion of said admixturehaving a known weight by: treating said portion with ammonium hydroxide(NH OH) to solubilize the AgO and Ag O, and separating the soluble AgOand Ag O from the Ag; and weighing the Ag, whereby the Ag content ofsaid admixture may be calculated.

10. A method for determining the free silver (Ag), argentic oxide (AgO),and argentious oxide (Ag O) content of an admixture of Ag, AgO, and AgO, wherein the AgO content is determined by the method of claim 7.

11. A method for determining the capacity of a battery having a silveroxide electrode without a destructive discharge, comprising:

placing at least one additional electrode that has been manufactured andprocessed like that in the battery in a sealed compartment in thebattery;

removing at least one of said additional electrodes from said sealedcompartment; and

analyzing said removed electrode for its free silver (Ag), argenticoxide (AgO), and argentous oxide (Ag O) content by the method of claim10.

References Cited UNITED STATES PATENTS 1,407,489 2/1922 Shakespeare136-82 2,767,063 10/1956 Chesncy 23-230 2,988,590 6/1961 Andr 13682OTHER REFERENCES MORRIS O. WOLK, Primary Examiner;

S. MARANTZ, Assistant Examiner.

US. Cl. X.R. 136-182

